Electrode-atomizer assembly for production of gaseous metal halides

ABSTRACT

An electrode-atomizer assembly is provided for use in generating vaporous metal halides using cosummable wire electrodes to form an electric arc in which the wire electrodes are melted and then atomized by a gas which reacts with the atomized metal, the electrode-atomizer assembly comprising improved guide means for feeding the wire electrodes into a reaction chamber; and resilient, electrically energized electrode contact means arranged to continuously engage the wire electrodes as they are fed into the reaction chamber.

Minted States Patent [1 1 [111 3,873,842

Thackara 1 Mar. 25, 1975 [54] ELECTRODILATOMIZER ASSEMBLY FOR 2,616,843 11/1952 Sheer ct a] 423/136 PRODUCTION OF GASEOUS METAL 2,677,771 5/1954 Turner 315/111 HALIDES 3,522,167 7/1970 Allen 250/542 3,734,761 5/1973 Becker et a1 106/300 [75] inventor: William C. Thackara, Brunswick,

173] Assignee: N L Industries, Inc, New York,

1132] Filed: Aug. 27, 1973 1211 Appl No.: 391,855

[5] 15.5. C1 250/544, 106/300, 204/164, 250/542. 423/136 151] int. Cl. C22d 7/08, C09c 1/62, COlf 7/00 1158] Field of Search 250/542, 544; 423/136; 204/164; 106/300 [56] References Cited UNITED STATES PATENTS 1224.788 5/1917 Reid 250/544 X 1.933.343 10/1933 Sandelowsky 315/111 X Primary Examiner-John H. Mack Assistant Examiner-Aaron Weisstuch [5 7] ABSTRACT An electrode-atomizer assembly is provided for use in generating vaporous metal halides using cosummable wire electrodes to form an electric arc in which the wire electrodes are melted and then atomized by a gas which reacts with the atomized metal, the electrodeatomizer assembly comprising improved guide means for feeding the wire electrodes into a reaction chamber; and resilient, electrically energized electrode contact means arranged to continuously engage the wire electrodes as they are fed into the reaction chamber.

1 Claim, 4 Drawing Figures ELECTRODE-ATOMIZER ASSEMBLY FOR PRODUCTION OF GASEOUS METAL HALIDES BACKGROUND OF INVENTION US Pat. No. 3,734,761 issued May 22, 1973 to Becker et al and assigned to Assignee of the instant invention describes a continuous method for forming vaporous metal halides wherein the metal, in the form of two consummable wire electrodes, is fed into a reaction chamber in which an arc is struck between the wire electrodes causing the latter to melt, the molten metal being immediately atomized by an inert gas in the presence of a gaseous halide, or by the gaseous halide itself, to form a gaseous metal halide accompanied by the evolution of considerable exothermic heat. The process of the above identified patent is directed specifically to the production of gaseous aluminum chloride for use in CUHJUHCIIOH with the production of titanium dioxide pigment by the so-called vapor phase process; and the simplicity and economics ofthe process have been such that it is being used commercially and constitutes an important advance in the art. However, the apparatus used in that invention embodies electrode guide means which also constitute the electrical conductors for transmitting electrical energy to the wire electrodes; and electrical contact with the wire electrodes is made within the reaction chamber where ahigh temperature, corrosne atmosphere exists. As a consequence, the arcing of the metal electrodes has been subject, at times, to erratic operation.

SUMMARY OF INVENTION The present invention relates to an improved electrodeatomizer assembly for use in the production of gaseous metal halides, the construction of the improved electrode-atomizer assembly of this invention being based on the discovery that the current carrying capability of a moving wire electrode is greatly in excess of the published values for the static current capacity of the wire. In light of this discovery the improved electrode-atomizer assembly of this invention is characterized by wire electrode guide means so designed that electrical contact with the wire electrodes is made outside the reaction chamber, the electrode contact means comprising resiliently mounted contact blocks in constant and substantially uniform engagement with the moving wire electrode. As a consequence, the sometimes erratic arcing of the electrodes has been eliminated. Moreover, the portion ofthe electrode guide means that enters the metal halide reaction chamber is formed ofa refractory material which effectively resists corrosion and/or malfunctioning in the hot atmosphere within the reaction chamber.

DESCRIPTION OF DRAWINGS FIG. 1 is a vertical elevation, partly in section, of the improved electrode-atomizer assembly of this inven tion shown mounted on the cover plate of a reaction chamber, a fragmentary portion of which is shown in section.

FIG. 2 is an enlarged longitudinal elevation in section in one of the composite wire electrode guide means of this invention:

FIG. 3 is a vertical elevation of the improved electrical contact means; and

FIG. 4 is a vertical elevation, partly in section, of the improved electrical contact means on line 4-4 of FIG. 3.

Referring to the drawing, the reaction chamber, in which the vaporous metal halide is formed, is indicated at 10 and has a cover plate 11 formed of a heat and corrosion resistant material such as, for example, lnconel metal and is provided with apertures 12-12 and 13. The longitudinal axis of the aperature 13 is substantially perpendicular to the plane of the cover plate 11 while the longitudinal axes of apertures l2-12, on opposite sides, respectively, of aperture 13, are each formed at an acute angle to the plane ofthe cover plate such that the angle included between the longitudinal axes of the apertures 1212 is less than and preferably about 45. The aperture 13 is provided with counterbores on the inside and outside surface, respectively, of the cover plate, the inner counterbore constituting a seat for one end of a refractory sleeve 14; and the outer counterbore a seat for one end of a tubular metal fitting 15. Each aperture 12 is formed with acounterbore on the outer surface of the cover plate which constitutes a seat for the corresponding end of a tubular metal fitting 16 designed to support one of the two electrode guide means hereinafter described, said tubular metal fittings l616 being sometimes referred to hereinafter and in the claims as supporting means therefor. To this end the lower end of each fitting 16 is welded or otherwise secured in its counterbored seat in the cover plate; and its upper end is threaded externally and provided with an internally threaded cap, indicated generally as 17, provided with a central aper ture 18. Each fitting 16 is provided, further, with a refractory lining or sleeve 19; and with a gas seal in the form of heat-resistant packing 20 as, for example, a Teflon washer between the end of the refractory sleeve 19 and the inner surface of the cap 17.

The aforesaid metal fitting 15 of the central aperture 13 is welded or otherwise fixedly secured in its seat and provided at its opposite end with an apertured, threaded cap with gas seal; and is designed to rigidly support the corresponding end of a halogen feed tube 21. The latter is preferably formed of aheat resistant metal and extends downwardly through the fitting 15, through the aperture 13 in the cover plate and into the refractory sleeve 14 where the feed tube 21 terminates just short of the lower end of refractory sleeve. The op posite or upper end of the feed tube 21 is connected, by suitable fittings 22 to one end of a flexible tube 23 adapted to supply a halogen gas, as for example gaseous chlorine, to the feed tube 21.

Turning now to the electrode guide means, of which there are two, one for each of the wire electrodes, these are identical and hence the following description of one will suffice for both. As shown especially well in FIGS. 1 and 2 each electrode guide means comprises a comi osite structure indicated generally at 24 in FIG. 2 and comprises: (1) an elongated ceramic or refractory tubular member 25, the inner end of which, ie the end adapted to extend into the reaction chamber, is bevelled, its opposite end being reduced in diameter to form an annular shoulder 27', and (2) an elongated metal tubular member 28 having'the same outside diameter and the same longitudinal bore as the ceramic member 25, the elongated metal tubular member 28 being reduced in diameter intermediate its opposite ends to form an annular shoulder 29. The outer end of the elongated metal tubular member 28 is provided with external threads 30 and a countersink 31. Also, a radial aperture 32 is formed therein substantially midway of the opposite ends of the tubular member 28 for accomodating a fitting 33 for feeding an inert gas into the electrode guide means. The two tubular members i.e. the ceramic member 25 and the elongated metal member 28 are adapted to be assembled on a common longitudinal axis with their reduced ends in abutting relationship in which position they are held securely by means of a metal sleeve 34. The latter is fitted onto the reduced portions of the respectively tubular members and is welded or otherwise secured at one end to the metal tubular member 28 and secured at its opposite end to the ceramic tubular member by a pin 35 or equivalent fastening means.

This composite electrode guide means is adapted to be assembled in the aforesaid supporting means 16 as shown in Fl(]. 1 in which it makes a close fit in the refractory sleeve 19, and is sealed against the escape of gas by the tightly fitting packing 20. As thus assembled the bevelled end of the ceramic tubular portion 25 of the electrode guide means extends into the reaction chamber 10. The opposite end of the electrode guide means extends through the apertured cap 17 ofthe supporting means 16 and is provided at its outer extremity with an apertured cap 36 threadedly secured thereon. The latter serves to hold suitable packing material in the aforesaid countersink 31 to form a gas seal at this end of the electrode guide means.

The resilient electrode contact means of which there are two. one for each wire electrode. is indicated generally at 37. As shown especially in FIGS. 3 and 4 each electrode guide means comprises a pair of elongated metal contact blocks 38 and 39, each substantially rectangular in cross-section and adapted to be mounted in superposed relationship on opposite sides of a wire electrode. the one block 39 being provided on its inner face with a longitudinally extending wire electrode guide groove 40. The opposite or outer face of this same block engages a metal terminal block -ll to which it is fixedly secured by a pair of pins 42-42 (see FIG. 3). the terminal block 41 having a terminal post 43 extending outwardly substantially perpendicularly from its outer face. The other of the two superposed contact blocks. that is to say the block 38. is adapted to be resiliently mounted with respect to its companion block 39. To this end two pairs of posts 44-44 are secured in axially aligned apertures of the contact block 39 and terminal block 41. said pairs of posts being substantially perpendicular to said blocks and at opposite ends thereof. and suitable apertures are provided at corresponding ends of the contact block 38 to slidably accommodate the posts 44-44. The top of each post 44 is provided with a retaining cap 45; and a coil spring 46 is mounted on each post between its retaining cap 45 and block 38 whereby the latter is resiliently urged by the springs 46-46 against the grooved face of its companion contact block 39.

Referring especially to FIG. 4 the resiliently mounted contacted block 38 is provided centrally of its outer face with a machine screw or similar fastening means 47 which is adapted to secure a flat braided electric cable 48, preferably at its midsection. to the contact block 38. The two free ends of the flat braided electric cable are then adapted to be brought down around opposite sides. respectively, of the resilient electrode contact means and to be secured to its terminal post 43 by a clamp 49.

The resilient electrical contact means hereinabove described is adapted to be supported by the electrode guide means hereinabove described and to this end the terminal block 41 is welded or otherwise secured to the apertured metal cap 36 of the electrode guide means after first aligning the wire electrode guide groove in contact block 39 of the electrical contact means with the longitudinal bore of the electrode guide means.

The wire electrodes are indicated at 50-50 and comprise metal wires adapted to be continuously fed to the electrode-atomizer assembly hereinabove described from suitable supply rolls and wire straightening rolls of conventional construction (not shown The wire electrodes are fed from the straightening rolls into flexible conduits. indicated at 51-51 which are secured to longitudinally apertured fittings 52-52 welded or otherwise secured to corresponding ends of the terminal blocks 41-41, the electrode guide grooves in the contact blocks 39-39 and the bores of the electrode guide means 24-24 all being in axial alignment and of a diameter only slightly greater than that of the wire electrodes whereby the latter are free to slide therethrough into the reaction chamber, the resiliently mounted contact blocks 38-38 of the electrode contact means being constantly urged by their respective coil springs into good electrical contact with the respective wire electrodes. The resiliently mounted electrode contact block means and guide groove provide additional straightening of the wire electrodes in order to remove any irregularities remaining after the above-mentioned conventional wire straightening process.

The operation of the improved electrode-atomizer assembly of this invention may be described briefly as follows: an inert gas. such as nitrogen. is fed into the wire electrode guide means 26 by way of the radial fitting 33 so as to pre\ent the leakage into the surrounding atmosphere of a halogen gas which is fed by way of feed tubes 23 and Zl into the reaction chamber [0 where it issues at a point substantially midway between the ceramic ends of the electrode guide means the feed tube 21 being protected by the surrounding refractory sleeve 14. The wire electrodes are fed continuously from feed rolls through the resiliently mounted electrode contact blocks and the electrode guide means into the reaction chamber. The resiliently mounted electrode contact blocks are energized by electric current from an electric source. indicated generally at 54, and due to the current carrying capability of the moving wire electrodes an electric arc is formed and maintained within the reaction chamber at substantially the point of intersection of the wire electrodes. As a consequence the electrodes are melted and simultaneously the molten metal is atomized by the gaseous halide issuing from the gas feed pipe 21 whereby the gaseous halide reacts with the atomized molten metal to produce a gaseous metal halide.

The electrode-atomizer assembly of this invention has been used successfully to produce gaseous aluminum chloride wherein the wire electrodes comprised aluminum metal and the atomizing gas was gaseous chlorine. the wire electrodes being fed into the reaction chamber at the rate of 29 ft. per minute per wire of 0.128 inches diameter and the chlorine gas being fed into the reaction chamber at the rate of 22 cu. ft. per

minute to produce gaseous aluminum chloride at a rate of about 4.4 lbs. per minute. It will be understood, however. that the apparatus of this invention is not limited to the production of gaseous aluminum chloride but is equally useful in the production of other metal halides.

l claim:

l. A consumable wire electrode atomizer assembly for producing gaseous metal halides in a reaction chamber having a cover plate, said consumable wire electrode 4 atomizer assembly comprising: support means fixedly secured to said cover plate exteriorly of said reaction chamber, said support means constructed and arranged (l) to support two wire electrode guide means in converging relationship and (2) a gas feed tube for feeding an atomizing gas into said reaction chamber. said gas feed tube support means being located between the support means of said two wire electrode guide means and arranged to support said gas feed tube with its inner end extending through an aperture in said cover plate into said reaction chamber, and a refractory sleeve secured on the underside of said cover plate and arranged to surround the said inner end of said gas feed tube; each of said wire electrode guide means being a composite structure comprising a tubular ceramic member, a tubular metal member and a metal sleeve wherein each of said tubular members has a bore dimensioned to accomodate a consumable wire electrode with a smooth sliding fit and the said metal sleeve lS arranged to secure said tubular members in axial alignment with adjacent ends in abutting relationship. the tubular ceramic member of each wire electrode guide means being arranged to extend through an aperture in said cover plate into said reaction chamber to support a consumable wire electrode therein in proxlmity to the inner end of said gas feed tube; means arranged to assemble each of said wire electrode guide means in one of the fixed support means on said cover plate, each of said assembly means comprising a refractory sleeve arranged to fit snugly in its respective support means and having a bore dimensioned to receive one of said composite wire electrode guide means with a close fit, and packing in each support means arranged to form a gas tight seal between its refractory sleeve and its composite wire electrode guide means; and a pair of wire electrode contact means each arranged to maintain continuous electrical contact with one of said consumable wire electrodes, each of said wire electrode contact means comprising a pair of metal contact blocks arranged to be supported in superposed relationship on a terminal block secured to one of said wire electrode guide means, one of said wire electrode contact blocks of a pair of said blocks having a longitudinally extending wire electrode guiding and straightening groove in its face opposite the corresponding face of its second block, and resilient means arranged to urge the opposed faces of each pair of said electrode contact blocks together continuously thereby to slidingly embrace a consumable wire electrode therebetween; wire electrode feed means arranged to feed a consumable wire electrode continuously from a supply roll through each of the pair of resiliently mounted contact blocks and the corresponding electrode guide means into said reaction chamber; and electric current carrying means connected to each terminal block whereby current is conducted to each consumable wire electrode by way of its respective pair of contact blocks to form an arc between the consumable electrodes in said reaction chamber in the presence ofsaid atomizing 

1. A consumable wire electrode - atomizer assembly for producing gaseous metal halides in a reaction chamber having a cover plate, said consumable wire electrode - atomizer assembly comprising: support means fixedly secured to said cover plate exteriorly of said reaction chamber, said support means constructed and arranged (1) to support two wire electrode guide means in converging relationship and (2) a gas feed tube for feeding an atomizing gas into said reaction chamber, said gas feed tube support means being located between the support means of said two wire electrode guide means and arranged to support said gas feed tube with its inner end extending through an aperture in said cover plate into said reaction chamber, and a refractory sleeve secured on the underside of said cover plate and arranged to surround the said inner end of said gas feed tube; each of said wire electrode guide means being a composite strucTure comprising a tubular ceramic member, a tubular metal member and a metal sleeve wherein each of said tubular members has a bore dimensioned to accomodate a consumable wire electrode with a smooth sliding fit and the said metal sleeve is arranged to secure said tubular members in axial alignment with adjacent ends in abutting relationship, the tubular ceramic member of each wire electrode guide means being arranged to extend through an aperture in said cover plate into said reaction chamber to support a consumable wire electrode therein in proximity to the inner end of said gas feed tube; means arranged to assemble each of said wire electrode guide means in one of the fixed support means on said cover plate, each of said assembly means comprising a refractory sleeve arranged to fit snugly in its respective support means and having a bore dimensioned to receive one of said composite wire electrode guide means with a close fit, and packing in each support means arranged to form a gas tight seal between its refractory sleeve and its composite wire electrode guide means; and a pair of wire electrode contact means each arranged to maintain continuous electrical contact with one of said consumable wire electrodes, each of said wire electrode contact means comprising a pair of metal contact blocks arranged to be supported in superposed relationship on a terminal block secured to one of said wire electrode guide means, one of said wire electrode contact blocks of a pair of said blocks having a longitudinally extending wire electrode guiding and straightening groove in its face opposite the corresponding face of its second block, and resilient means arranged to urge the opposed faces of each pair of said electrode contact blocks together continuously thereby to slidingly embrace a consumable wire electrode therebetween; wire electrode feed means arranged to feed a consumable wire electrode continuously from a supply roll through each of the pair of resiliently mounted contact blocks and the corresponding electrode guide means into said reaction chamber; and electric current carrying means connected to each terminal block whereby current is conducted to each consumable wire electrode by way of its respective pair of contact blocks to form an arc between the consumable electrodes in said reaction chamber in the presence of said atomizing gas. 